If you haven't heard, Twitpic applied for a trademark, and Twitter filed for an opposition. Opposition means you oppose a trademark from becoming registered in the US. Unfortunately, it looks like Twitpic couldn't defend the opposition against a big company like Twitter. If you look at the procedural history here, it's a pretty short one. (You'll see that Twitter filed for an opposition and that was that.)

What's really interesting is that Twitpic operated for about 3 years until Twitter added a function to add photos and videos to tweets in 2011. Twitpic filed a trademark application in August 2009, abandoned the application, filed a second trademark application in October 2009, abandoned that application, and filed a third trademark application in October 2013. Then Twitter filed for a request for an extension of time on the last day before the filing for an opposition was due, and another request for an extension of time on the last day before the filing for the opposition was due.

It looks like Twitpic had some time to prepare for the opposition, but I guess they still didn't have sufficient means to defend itself. I'm surprised that Twitpic would be confused with Twitter. It's too bad that Twitpic had to resort to closing down its business after drastically changing the way we share information... via Twitter, no less.